537 lines
19 KiB
Rust
537 lines
19 KiB
Rust
//! Conditional compilation stripping.
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use rustc_ast::attr::HasAttrs;
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use rustc_ast::mut_visit::*;
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use rustc_ast::ptr::P;
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use rustc_ast::{self as ast, AttrItem, Attribute, MetaItem};
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use rustc_attr as attr;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_data_structures::map_in_place::MapInPlace;
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use rustc_errors::{error_code, struct_span_err, Applicability, Handler};
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use rustc_feature::{Feature, Features, State as FeatureState};
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use rustc_feature::{
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ACCEPTED_FEATURES, ACTIVE_FEATURES, REMOVED_FEATURES, STABLE_REMOVED_FEATURES,
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};
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use rustc_parse::{parse_in, validate_attr};
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use rustc_session::parse::feature_err;
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use rustc_session::Session;
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use rustc_span::edition::{Edition, ALL_EDITIONS};
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use rustc_span::symbol::{sym, Symbol};
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use rustc_span::{Span, DUMMY_SP};
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use smallvec::SmallVec;
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/// A folder that strips out items that do not belong in the current configuration.
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pub struct StripUnconfigured<'a> {
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pub sess: &'a Session,
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pub features: Option<&'a Features>,
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}
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fn get_features(
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sess: &Session,
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span_handler: &Handler,
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krate_attrs: &[ast::Attribute],
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) -> Features {
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fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
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let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
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err.span_label(span, "feature has been removed");
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if let Some(reason) = reason {
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err.note(reason);
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}
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err.emit();
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}
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fn active_features_up_to(edition: Edition) -> impl Iterator<Item = &'static Feature> {
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ACTIVE_FEATURES.iter().filter(move |feature| {
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if let Some(feature_edition) = feature.edition {
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feature_edition <= edition
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} else {
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false
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}
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})
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}
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let mut features = Features::default();
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let mut edition_enabled_features = FxHashMap::default();
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let crate_edition = sess.edition();
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for &edition in ALL_EDITIONS {
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if edition <= crate_edition {
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// The `crate_edition` implies its respective umbrella feature-gate
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// (i.e., `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
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edition_enabled_features.insert(edition.feature_name(), edition);
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}
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}
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for feature in active_features_up_to(crate_edition) {
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feature.set(&mut features, DUMMY_SP);
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edition_enabled_features.insert(feature.name, crate_edition);
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}
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// Process the edition umbrella feature-gates first, to ensure
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// `edition_enabled_features` is completed before it's queried.
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for attr in krate_attrs {
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if !sess.check_name(attr, sym::feature) {
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continue;
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}
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let list = match attr.meta_item_list() {
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Some(list) => list,
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None => continue,
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};
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for mi in list {
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if !mi.is_word() {
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continue;
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}
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let name = mi.name_or_empty();
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let edition = ALL_EDITIONS.iter().find(|e| name == e.feature_name()).copied();
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if let Some(edition) = edition {
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if edition <= crate_edition {
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continue;
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}
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for feature in active_features_up_to(edition) {
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// FIXME(Manishearth) there is currently no way to set
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// lib features by edition
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feature.set(&mut features, DUMMY_SP);
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edition_enabled_features.insert(feature.name, edition);
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}
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}
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}
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}
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for attr in krate_attrs {
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if !sess.check_name(attr, sym::feature) {
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continue;
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}
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let list = match attr.meta_item_list() {
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Some(list) => list,
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None => continue,
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};
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let bad_input = |span| {
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struct_span_err!(span_handler, span, E0556, "malformed `feature` attribute input")
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};
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for mi in list {
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let name = match mi.ident() {
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Some(ident) if mi.is_word() => ident.name,
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Some(ident) => {
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bad_input(mi.span())
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.span_suggestion(
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mi.span(),
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"expected just one word",
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format!("{}", ident.name),
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Applicability::MaybeIncorrect,
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)
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.emit();
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continue;
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}
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None => {
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bad_input(mi.span()).span_label(mi.span(), "expected just one word").emit();
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continue;
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}
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};
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if let Some(edition) = edition_enabled_features.get(&name) {
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let msg =
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&format!("the feature `{}` is included in the Rust {} edition", name, edition);
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span_handler.struct_span_warn_with_code(mi.span(), msg, error_code!(E0705)).emit();
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continue;
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}
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if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
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// Handled in the separate loop above.
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continue;
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}
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let removed = REMOVED_FEATURES.iter().find(|f| name == f.name);
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let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.name);
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if let Some(Feature { state, .. }) = removed.or(stable_removed) {
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if let FeatureState::Removed { reason } | FeatureState::Stabilized { reason } =
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state
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{
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feature_removed(span_handler, mi.span(), *reason);
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continue;
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}
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}
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if let Some(Feature { since, .. }) = ACCEPTED_FEATURES.iter().find(|f| name == f.name) {
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let since = Some(Symbol::intern(since));
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features.declared_lang_features.push((name, mi.span(), since));
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continue;
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}
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if let Some(allowed) = sess.opts.debugging_opts.allow_features.as_ref() {
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if allowed.iter().find(|&f| name.as_str() == *f).is_none() {
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struct_span_err!(
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span_handler,
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mi.span(),
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E0725,
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"the feature `{}` is not in the list of allowed features",
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name
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)
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.emit();
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continue;
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}
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}
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if let Some(f) = ACTIVE_FEATURES.iter().find(|f| name == f.name) {
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f.set(&mut features, mi.span());
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features.declared_lang_features.push((name, mi.span(), None));
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continue;
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}
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features.declared_lib_features.push((name, mi.span()));
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}
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}
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features
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}
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// `cfg_attr`-process the crate's attributes and compute the crate's features.
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pub fn features(sess: &Session, mut krate: ast::Crate) -> (ast::Crate, Features) {
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let mut strip_unconfigured = StripUnconfigured { sess, features: None };
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let unconfigured_attrs = krate.attrs.clone();
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let diag = &sess.parse_sess.span_diagnostic;
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let err_count = diag.err_count();
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let features = match strip_unconfigured.configure(krate.attrs) {
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None => {
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// The entire crate is unconfigured.
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krate.attrs = Vec::new();
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krate.module.items = Vec::new();
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Features::default()
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}
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Some(attrs) => {
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krate.attrs = attrs;
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let features = get_features(sess, diag, &krate.attrs);
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if err_count == diag.err_count() {
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// Avoid reconfiguring malformed `cfg_attr`s.
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strip_unconfigured.features = Some(&features);
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strip_unconfigured.configure(unconfigured_attrs);
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}
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features
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}
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};
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(krate, features)
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}
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#[macro_export]
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macro_rules! configure {
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($this:ident, $node:ident) => {
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match $this.configure($node) {
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Some(node) => node,
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None => return Default::default(),
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}
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};
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}
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const CFG_ATTR_GRAMMAR_HELP: &str = "#[cfg_attr(condition, attribute, other_attribute, ...)]";
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const CFG_ATTR_NOTE_REF: &str = "for more information, visit \
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<https://doc.rust-lang.org/reference/conditional-compilation.html\
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#the-cfg_attr-attribute>";
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impl<'a> StripUnconfigured<'a> {
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pub fn configure<T: HasAttrs>(&mut self, mut node: T) -> Option<T> {
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self.process_cfg_attrs(&mut node);
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self.in_cfg(node.attrs()).then_some(node)
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}
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/// Parse and expand all `cfg_attr` attributes into a list of attributes
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/// that are within each `cfg_attr` that has a true configuration predicate.
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///
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/// Gives compiler warnings if any `cfg_attr` does not contain any
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/// attributes and is in the original source code. Gives compiler errors if
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/// the syntax of any `cfg_attr` is incorrect.
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pub fn process_cfg_attrs<T: HasAttrs>(&mut self, node: &mut T) {
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node.visit_attrs(|attrs| {
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attrs.flat_map_in_place(|attr| self.process_cfg_attr(attr));
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});
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}
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/// Parse and expand a single `cfg_attr` attribute into a list of attributes
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/// when the configuration predicate is true, or otherwise expand into an
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/// empty list of attributes.
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///
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/// Gives a compiler warning when the `cfg_attr` contains no attributes and
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/// is in the original source file. Gives a compiler error if the syntax of
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/// the attribute is incorrect.
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fn process_cfg_attr(&mut self, attr: Attribute) -> Vec<Attribute> {
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if !attr.has_name(sym::cfg_attr) {
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return vec![attr];
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}
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let (cfg_predicate, expanded_attrs) = match self.parse_cfg_attr(&attr) {
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None => return vec![],
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Some(r) => r,
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};
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// Lint on zero attributes in source.
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if expanded_attrs.is_empty() {
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return vec![attr];
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}
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// At this point we know the attribute is considered used.
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self.sess.mark_attr_used(&attr);
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if !attr::cfg_matches(&cfg_predicate, &self.sess.parse_sess, self.features) {
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return vec![];
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}
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// We call `process_cfg_attr` recursively in case there's a
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// `cfg_attr` inside of another `cfg_attr`. E.g.
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// `#[cfg_attr(false, cfg_attr(true, some_attr))]`.
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expanded_attrs
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.into_iter()
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.flat_map(|(item, span)| {
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let attr = attr::mk_attr_from_item(attr.style, item, span);
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self.process_cfg_attr(attr)
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})
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.collect()
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}
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fn parse_cfg_attr(&self, attr: &Attribute) -> Option<(MetaItem, Vec<(AttrItem, Span)>)> {
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match attr.get_normal_item().args {
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ast::MacArgs::Delimited(dspan, delim, ref tts) if !tts.is_empty() => {
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let msg = "wrong `cfg_attr` delimiters";
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validate_attr::check_meta_bad_delim(&self.sess.parse_sess, dspan, delim, msg);
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match parse_in(&self.sess.parse_sess, tts.clone(), "`cfg_attr` input", |p| {
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p.parse_cfg_attr()
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}) {
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Ok(r) => return Some(r),
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Err(mut e) => {
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e.help(&format!("the valid syntax is `{}`", CFG_ATTR_GRAMMAR_HELP))
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.note(CFG_ATTR_NOTE_REF)
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.emit();
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}
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}
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}
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_ => self.error_malformed_cfg_attr_missing(attr.span),
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}
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None
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}
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fn error_malformed_cfg_attr_missing(&self, span: Span) {
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self.sess
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.parse_sess
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.span_diagnostic
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.struct_span_err(span, "malformed `cfg_attr` attribute input")
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.span_suggestion(
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span,
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"missing condition and attribute",
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CFG_ATTR_GRAMMAR_HELP.to_string(),
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Applicability::HasPlaceholders,
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)
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.note(CFG_ATTR_NOTE_REF)
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.emit();
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}
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/// Determines if a node with the given attributes should be included in this configuration.
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pub fn in_cfg(&self, attrs: &[Attribute]) -> bool {
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attrs.iter().all(|attr| {
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if !is_cfg(self.sess, attr) {
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return true;
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}
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let meta_item = match validate_attr::parse_meta(&self.sess.parse_sess, attr) {
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Ok(meta_item) => meta_item,
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Err(mut err) => {
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err.emit();
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return true;
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}
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};
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let error = |span, msg, suggestion: &str| {
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let mut err = self.sess.parse_sess.span_diagnostic.struct_span_err(span, msg);
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if !suggestion.is_empty() {
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err.span_suggestion(
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span,
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"expected syntax is",
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suggestion.into(),
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Applicability::MaybeIncorrect,
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);
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}
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err.emit();
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true
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};
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let span = meta_item.span;
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match meta_item.meta_item_list() {
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None => error(span, "`cfg` is not followed by parentheses", "cfg(/* predicate */)"),
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Some([]) => error(span, "`cfg` predicate is not specified", ""),
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Some([_, .., l]) => error(l.span(), "multiple `cfg` predicates are specified", ""),
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Some([single]) => match single.meta_item() {
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Some(meta_item) => {
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attr::cfg_matches(meta_item, &self.sess.parse_sess, self.features)
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}
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None => error(single.span(), "`cfg` predicate key cannot be a literal", ""),
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},
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}
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})
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}
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/// Visit attributes on expression and statements (but not attributes on items in blocks).
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fn visit_expr_attrs(&mut self, attrs: &[Attribute]) {
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// flag the offending attributes
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for attr in attrs.iter() {
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self.maybe_emit_expr_attr_err(attr);
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}
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}
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/// If attributes are not allowed on expressions, emit an error for `attr`
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pub fn maybe_emit_expr_attr_err(&self, attr: &Attribute) {
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if !self.features.map(|features| features.stmt_expr_attributes).unwrap_or(true) {
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let mut err = feature_err(
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&self.sess.parse_sess,
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sym::stmt_expr_attributes,
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attr.span,
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"attributes on expressions are experimental",
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);
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if attr.is_doc_comment() {
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err.help("`///` is for documentation comments. For a plain comment, use `//`.");
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}
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err.emit();
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}
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}
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pub fn configure_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
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let ast::ForeignMod { unsafety: _, abi: _, items } = foreign_mod;
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items.flat_map_in_place(|item| self.configure(item));
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}
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fn configure_variant_data(&mut self, vdata: &mut ast::VariantData) {
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match vdata {
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ast::VariantData::Struct(fields, ..) | ast::VariantData::Tuple(fields, _) => {
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fields.flat_map_in_place(|field| self.configure(field))
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}
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ast::VariantData::Unit(_) => {}
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}
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}
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pub fn configure_item_kind(&mut self, item: &mut ast::ItemKind) {
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match item {
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ast::ItemKind::Struct(def, _generics) | ast::ItemKind::Union(def, _generics) => {
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self.configure_variant_data(def)
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}
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ast::ItemKind::Enum(ast::EnumDef { variants }, _generics) => {
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variants.flat_map_in_place(|variant| self.configure(variant));
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for variant in variants {
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self.configure_variant_data(&mut variant.data);
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}
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}
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_ => {}
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}
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}
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pub fn configure_expr_kind(&mut self, expr_kind: &mut ast::ExprKind) {
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match expr_kind {
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ast::ExprKind::Match(_m, arms) => {
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arms.flat_map_in_place(|arm| self.configure(arm));
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}
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ast::ExprKind::Struct(_path, fields, _base) => {
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fields.flat_map_in_place(|field| self.configure(field));
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}
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_ => {}
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}
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}
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pub fn configure_expr(&mut self, expr: &mut P<ast::Expr>) {
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self.visit_expr_attrs(expr.attrs());
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// If an expr is valid to cfg away it will have been removed by the
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// outer stmt or expression folder before descending in here.
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// Anything else is always required, and thus has to error out
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// in case of a cfg attr.
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//
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// N.B., this is intentionally not part of the visit_expr() function
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// in order for filter_map_expr() to be able to avoid this check
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if let Some(attr) = expr.attrs().iter().find(|a| is_cfg(self.sess, a)) {
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let msg = "removing an expression is not supported in this position";
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self.sess.parse_sess.span_diagnostic.span_err(attr.span, msg);
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}
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self.process_cfg_attrs(expr)
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}
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pub fn configure_pat(&mut self, pat: &mut P<ast::Pat>) {
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if let ast::PatKind::Struct(_path, fields, _etc) = &mut pat.kind {
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fields.flat_map_in_place(|field| self.configure(field));
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}
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}
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pub fn configure_fn_decl(&mut self, fn_decl: &mut ast::FnDecl) {
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fn_decl.inputs.flat_map_in_place(|arg| self.configure(arg));
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}
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}
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impl<'a> MutVisitor for StripUnconfigured<'a> {
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fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
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self.configure_foreign_mod(foreign_mod);
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noop_visit_foreign_mod(foreign_mod, self);
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}
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fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
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self.configure_item_kind(item);
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noop_visit_item_kind(item, self);
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}
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fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
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self.configure_expr(expr);
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self.configure_expr_kind(&mut expr.kind);
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noop_visit_expr(expr, self);
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}
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fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
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let mut expr = configure!(self, expr);
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self.configure_expr_kind(&mut expr.kind);
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noop_visit_expr(&mut expr, self);
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Some(expr)
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}
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fn flat_map_generic_param(
|
|
&mut self,
|
|
param: ast::GenericParam,
|
|
) -> SmallVec<[ast::GenericParam; 1]> {
|
|
noop_flat_map_generic_param(configure!(self, param), self)
|
|
}
|
|
|
|
fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
|
|
noop_flat_map_stmt(configure!(self, stmt), self)
|
|
}
|
|
|
|
fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
|
|
noop_flat_map_item(configure!(self, item), self)
|
|
}
|
|
|
|
fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
|
|
noop_flat_map_assoc_item(configure!(self, item), self)
|
|
}
|
|
|
|
fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
|
|
noop_flat_map_assoc_item(configure!(self, item), self)
|
|
}
|
|
|
|
fn visit_mac(&mut self, _mac: &mut ast::MacCall) {
|
|
// Don't configure interpolated AST (cf. issue #34171).
|
|
// Interpolated AST will get configured once the surrounding tokens are parsed.
|
|
}
|
|
|
|
fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
|
|
self.configure_pat(pat);
|
|
noop_visit_pat(pat, self)
|
|
}
|
|
|
|
fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
|
|
self.configure_fn_decl(&mut fn_decl);
|
|
noop_visit_fn_decl(fn_decl, self);
|
|
}
|
|
}
|
|
|
|
fn is_cfg(sess: &Session, attr: &Attribute) -> bool {
|
|
sess.check_name(attr, sym::cfg)
|
|
}
|